DE102018206343A1 - Process and plant for the mass production of hot formed sheet metal parts from a steel strip - Google Patents

Abstract

The invention relates to a method for the series production of hot-formed sheet-metal shaped parts (230), wherein the following steps are carried out at the stations (110, 120, 130, 140, 150) of a production line in the direction of the production flow (D):
Unwinding a steel strip (210) from a coil (220);
- Heating the steel strip (210), so that forms an austenitic structure;
- Pre-cooling of the steel strip (210);
- Producing boards from the pre-cooled steel sheet strip (210);
- Hot forming of the boards to sheet metal parts (230), trimming the sheet metal parts and form-calibrating the sheet metal parts using a plurality of successively arranged tools (151, 152, 153, 154, 155), wherein simultaneous cooling takes place during hot forming, trimming and / or mold calibration.
The invention further relates to a system (100) for carrying out this method, as well as an alternative embodiment of the method and the system.

Description

The invention relates to a method and a plant for mass production hot-formed sheet metal parts, in particular hot-formed body parts.

Serial production or series production means the production of the same products (here sheet metal parts) in one production line. A production line comprises a plurality of stations (production stations with operating means) arranged according to a predetermined production sequence, in particular simultaneously operated stations, on which the individual production steps are carried out in the direction of the predetermined production flow. The workpieces or products to be produced are thereby, in particular clock bound, passed from one to the next station.

In the context of the invention, hot forming means forming steps in which the sheet material is heated to a temperature above room temperature. For steel sheet material, the heating temperature may be several hundred degrees Celsius (i.e., at least 200 ° C), and the recrystallization temperature (about 550 ° C to 700 ° C) may be exceeded. As a result, with small forming forces large changes in shape are possible. In addition, the effect of structural changes can be used selectively to sheet metal parts with special properties, such. As a high strength to produce.

The DE 10 2009 012 940 B4 describes a production line with several processing stations for the production of hot-formed sheet metal components. In the processing stations, the sheet metal components are preformed cold blanks, pruned, heated, air-cooled, optionally hot post-formed and then cooled in at least one cooling tool.

The prior art is also on in the DE 10 2009 016 027 A1 described production line for hot forming.

The invention has for its object to provide a method and system for mass production of hot-formed sheet metal parts that do not have at least one associated with the prior art disadvantage or at least only reduced.

The object is achieved by the method according to the invention with the features of patent claim 1 (first method variant) and by an alternative method according to the invention having the features of patent claim 3 (second method variant). The object is further achieved by the inventive system with the features of claim 8 (first plant variant) and by an alternative inventive plant (second plant variant) with the features of claim 10. Further developments and embodiments of the invention are analogous to both subject of the invention from the dependent Claims, the following description of the invention and the figures.

• - Abwickeln eines Stahlblechbands von einem Coil (Bandstahlrolle);
• - Erwärmen, d. h. zumindest partielles Erwärmen, des Stahlblechbands, sodass sich (im Stahlblechband) ein austenitisches Gefüge bildet;
• - Vorkühlen des Stahlblechbands;
• - Erzeugen von Platinen aus dem vorgekühlten Stahlblechband;
• - Warmumformen der Platinen zu Blechformteilen, Beschneiden der Blechformteile und Formkalibrieren der Blechformteile mithilfe mehrerer, in Richtung des Fertigungsflusses nacheinander angeordneter Werkzeuge, insbesondere Pressenwerkzeuge, wobei beim Warmumformen, Beschneiden und/oder Formkalibrieren ein gleichzeitiges Abkühlen (des Stahlblechs), insbesondere mit einer gezielten Temperaturführung, erfolgt.

The first variant of the method according to the invention for mass production of hot-formed sheet-metal shaped parts provides that the following steps are carried out at the stations of a production line in the direction of the production flow:

• Unwinding a steel strip from a coil (strip steel roll);
• Heating, ie at least partial heating, of the steel strip so that an austenitic structure is formed (in the steel strip);
• - Pre-cooling of the steel strip;
• - Production of boards from the pre-cooled steel sheet strip;
• - Hot forming of the blanks to sheet metal parts, trimming the sheet metal parts and mold calibrating the sheet metal parts using several, in the direction of the production flow successively arranged tools, in particular press tools, wherein during hot forming, trimming and / or shape calibration simultaneous cooling (of the steel sheet), in particular with a targeted temperature control , he follows.

It is preferably provided that the blanks are produced from the precooled steel sheet strip by means of a shearing device (shears) or the like. The blanks produced with a guillotine have a simple, usually quadrangular outline and can also be referred to as tablets. By means of a cutting laser device, a cutting tool or the like, molded blanks can also be produced directly from the precooled sheet steel strip or from the sheets. For the board cutting a separate station (board cutting station) may be provided. However, the blank cut can also be made directly in a tool, in particular a press tool, which is arranged in the direction of the production flow in front of the first hot forming tool (for hot forming of the blanks).

• - Abwickeln eines Stahlblechbands von einem Coil;
• - Erwärmen des Stahlblechbands, sodass sich ein austenitisches Gefüge bildet;
• - Vorkühlen des Stahlblechbands;
• - Zuführen des vorgekühlten Stahlblechbands zu einer Folgeverbundwerkzeuggruppe mit mehreren Werkzeugstufen zum Warmumformen des Stahlblechbands zu Blechformteilen, Beschneiden der Blechformteile, Formkalibrieren der Blechformteile und Freischneiden der Blechformteile, wobei in wenigstens einer Werkzeugstufe ein gleichzeitiges Abkühlen, insbesondere mit einer gezielten Temperaturführung, erfolgt.

The second variant of the method according to the invention for mass production of hot-formed sheet-metal shaped parts provides that the following steps are carried out at the stations of a production line in the direction of the production flow:

• - Unwinding a steel strip from a coil;
• - Heating the steel strip so that forms an austenitic structure;
• - Pre-cooling of the steel strip;
• - Supplying the precooled steel strip to a progressive tool group with multiple tool stages for hot forming the steel strip to sheet metal parts, trimming the sheet metal parts, mold calibration of the sheet metal parts and free cutting of the sheet metal parts, wherein in at least one tool stage simultaneous cooling, in particular with a targeted temperature control occurs.

A follow-on composite tool group is understood to mean a tool group comprising a plurality of tool stages or individual tools, in particular press tools. In these tool stages, the shaped sheet metal parts are successively produced from the supplied, still warm sheet steel strip in time and thereby transported using at least one carrier strip. Finally, the sheet metal parts are separated from the carrier strip (free cutting). A previous board cut is not required.

The following explanations apply analogously to both process variants of the process according to the invention.

The steel sheet strip, while being moved through a heating station (eg at a speed of 12 m / min to 30 m / min), is at a temperature above the austenitizing temperature (> AC3, preferably ≥ 800 ° C, especially ≥ 900 ° C) and held above the austenitizing temperature (holding phase or holding time eg ≥ 30 s, preferably ≥ 45 s), so that a complete austenitic microstructure transformation takes place. Subsequently, the steel sheet strip is cooled to a lower temperature level (the pre-cooling temperature is in a range of 650 ° C to 750 ° C, for example) while being moved through a precooling station (the cooling time is 4 seconds to 6 seconds, for example). Undercooled austenite can form during this process. The shaped sheet metal parts are then shaped, cut and shape-calibrated from the precooled sheet steel strip, optionally after previous blank cutting, the steel sheet being at an insertion temperature (below the precooling temperature, eg between 400 C and 600 ° C., preferably between 450 ° C. and 550 ° C.) is cooled as rapidly to a target temperature (eg 180 ° C. to 220 ° C., whereby lower target temperatures are also possible), that a substantially martensitic microstructure or at least a martensitic microstructure is formed (the critical cooling rate is dependent on the steel sheet material or material and is for example at least 10 K / s and preferably at least 20 K / s). The martensitic transformation is accompanied by a strength or hardness increase. If the rapid cooling to the target temperature in a mold, this process can also be referred to as a form hardening. Cooling to target temperature preferably takes place only during mold calibration. The trimming and possibly provided punching operations are preferably carried out at a temperature between the insert temperature and the target temperature (eg in a temperature range between 300 ° C and 500 ° C), i. H. before the martensitic transformation begins or is completed. If the cooling to the target temperature occurs only during mold calibration, it may be necessary to heat the previous tools (for hot forming and trimming) if necessary. For the tools, a temperature control is preferably provided, in particular such that each temperature-controlled tool has its own control loop.

The preferred sheet material is a conversion-delayed manganese boron steel (eg 20MnB8) which has a broad cooling corridor for the martensitic hardening and therefore has very good precooling requirements.

The invention enables the series production of directly hot formed sheet metal parts (i.e., without cold preforming of the steel sheet material) with low cycle time, short cycle times and high output. In addition, energy savings are possible. In addition, tool-related finished parts can be produced.

The heating or heating of the steel strip can be done inductively, which allows a quick and rapid and precise heating. The heating station can for this purpose have a plurality of fixed and / or movable inductors, which operate as Längsfeldinduktoren and / or Querfeldinduktoren, as described in detail in the DE 10 2014 211 241 A1 described. The steel sheet strip, while being moved through the heating station, may be heated to about 750 ° C (approximately the Curie temperature) by means of at least one longitudinal field inductor (the heating time is, for example, 5 seconds to 15 seconds), and may then be accomplished using at least one transverse field inductor (which is arranged in the direction of the production flow behind the Längsfeldinduktor) continue to Austenitisierungstemperatur (> AC3, preferably ≥ 800 ° C, in particular ≥ 900 ° C) are heated (the heating time can then be another 5 s to 12 s). The holding phase can be realized by means of a continuous furnace belonging to the heating station, which passes through the steel sheet strip after its inductive heating or heating. The holding phase can also be realized by induction become. It can be provided that only strip-like areas of the steel strip are heated, thereby producing sheet metal parts with locally different strength properties (analogous to partial press hardening).

The precooling or intermediate cooling of the steel strip may be carried out convivially by means of at least one nozzle field where the steel strip is moved past and cooled by means of air (or gas), water or a multiphase mixture (eg air + water). The pre-cooling of the steel strip may also be conductive by means of at least one cooling roll or cooling plate on which the steel strip is moved past. Pre-cooling preferably takes place in a pre-cooling or intermediate cooling station. Preferably, a combination of at least one nozzle array and at least one cooling roller pair is provided.

The sheet steel strip can be cleaned during pre-cooling or after precooling to z. B to remove or at least reduce a scale or oxide layer. The cleaning can be done, for example, by high-pressure blasting, in particular with an abrasive agent, or by applying a reducing liquid. The cleaning can also be done by means of ultrasound. The cleaning is preferably carried out in the pre-cooling station, wherein the high-pressure jetting or the application of a reducing liquid can also serve for pre-cooling at the same time, d. that is, pre-cooling and cleaning can be combined. By means of cooling rollers, the scale and / or oxide layer to be removed can be broken up beforehand, which favors the removal. Alternatively, it can also be provided that the scale or oxide layer is not removed, but pressed and compacted, z. B. with the help of used cooling rollers, with the aim to leave them permanently on the sheet metal part, so that a later cleaning blasting can be omitted (especially in a zinc coating, see below).

The sheet steel strip can be bright. The steel strip may also have a zinc coating (zinc-containing protective coating), which is understood to mean, in particular, that the steel strip strip provided as a coil is already provided with a zinc coating or zinc coating applied in particular on both sides. The zinc coating can protect the steel sheet material from scaling and is suitable for both inductive heating and furnace heating and may even promote heating (by absorbing heat more quickly). An oxide layer or oxide skin forming on heating protects the zinc layer and can be removed later, as described above. Alternatively, it may be provided that the zinc coating is applied to the originally uncoated sheet steel strip only after the pre-cooling, in particular following a cleaning (descaling), z. B. by spraying or by immersion (hot dip galvanizing). This zinc coating or galvanizing may take place in the precooling station or in a separate coating station which is arranged in the direction of the production flow after the precooling station. The steel strip may also have an aluminum coating (eg, an aluminum-silicon coating) or other coating.

• - mindestens eine Station (Abwickelstation) zum Abwickeln eines Stahlblechbands von einem Coil;
• - mindestens eine Station (Erwärmungsstation) zum Erwärmen des Stahlblechbands;
• - mindestens eine Station (Vorkühlstation) zum Vorkühlen des Stahlblechbands;
• - mindestens eine Station (Platinenschnittstation), oder zumindest eine Vorrichtung oder ein Werkzeug, zum Erzeugen von Platinen aus dem vorgekühlten Stahlblechband;
• - mindestens eine Station (Formstation) zum Warmumformen der Platinen zu Blechformteilen, Beschneiden der Blechformteile und Formkalibrieren der Blechformteile, insbesondere mit Abkühlung, wie oben beschrieben.

The first variant of the plant according to the invention for the series production of hot-formed sheet-metal shaped parts has at least the following stations arranged in the direction of the production flow:

• - At least one station (unwinding) for unwinding a steel strip from a coil;
• - at least one station (heating station) for heating the steel strip;
• - at least one station (pre-cooling station) for pre-cooling the steel strip;
• - At least one station (board cutting station), or at least a device or a tool for producing boards from the pre-cooled steel sheet strip;
• - At least one station (forming station) for hot forming the boards to sheet metal parts, trimming the sheet metal parts and form calibrating the sheet metal parts, especially with cooling, as described above.

This system variant is suitable for carrying out the first method variant.

It is preferably provided that the station for hot forming, trimming and mold calibration forms an L arrangement with the other stations. This is understood to mean in particular that the stations for unwinding, heating, precooling and producing the boards, a heating line (first production line section) and the station for hot forming, trimming and shape calibration form a tool line (second production line section), wherein the heating line and the tool path are in a L Arrangement are arranged or each other have an L-shaped arrangement. In particular, it is provided that the station, or at least the device or the tool, forms the transition (corner point) for producing the boards.

• - mindestens eine Station (Abwickelstation) zum Abwickeln eines Stahlblechbands von einem Coil;
• - mindestens eine Station (Erwärmungsstation) zum Erwärmen des Stahlblechbands;
• - mindestens eine Station (Vorkühlstation) zum Vorkühlen des Stahlblechbands;
• - mindestens eine Station (Formstation) mit einer Folgeverbundwerkzeuggruppe, zum Warmumformen des Stahlblechbands zu Blechformteilen, Beschneiden der Blechformteile, Formkalibrieren der Blechformteile und Freischneiden der Blechformteile, insbesondere mit Abkühlung, wie oben beschrieben.

The second variant of the plant according to the invention for the series production of hot-formed sheet-metal shaped parts has at least the following stations arranged in the direction of the production flow:

• - at least one station (unwinding station) for unwinding a steel strip from a coil;
• - at least one station (heating station) for heating the steel strip;
• - at least one station (pre-cooling station) for pre-cooling the steel strip;
• - At least one station (forming station) with a follow-on composite tool group, for hot forming the steel strip to sheet metal parts, trimming the sheet metal parts, mold calibration of sheet metal parts and free cutting of sheet metal parts, especially with cooling, as described above.

This system variant is suitable for carrying out the second method variant.

Both system variants may according to the preceding explanations have other stations, such. B. a cleaning station and / or a coating station.

• 1 zeigt schematisch eine erste Ausführungsmöglichkeit der Erfindung, entsprechend der ersten Verfahrens- und Anlagenvariante.
• 2 zeigt schematisch eine zweite Ausführungsmöglichkeit der Erfindung, entsprechend der zweiten Verfahrens- und Anlagenvariante.

The invention will now be described by way of example and not by way of limitation with reference to the figures. The features shown in the figures and / or explained below may, even independently of specific combinations of features, be general features of the invention and further develop the invention accordingly.

• 1 schematically shows a first embodiment of the invention, according to the first method and equipment variant.
• 2 schematically shows a second embodiment of the invention, according to the second method and equipment variant.

In the 1 shown attachment 100 includes several stations 110 . 120 . 130 . 140 . 150 , which is a production line for the series production of hot formed sheet metal parts 230 form. The arrow D indicates the direction of the production flow.

In the first station (unwinding station) 110 becomes a steel sheet strip 210 from a coil 220 unwound and continuously or optionally also discontinuously moved on. In the second station (warming station) 120 becomes the steel sheet strip 210 heated to Austenitisierungstemperatur (ie, the steel sheet is directly from the coil 220 coming austenitized). The warming station 120 has both sides (ie above and below the steel strip moving therebetween 210 ) arranged inductors (induction devices) 121 and (at least) one in the direction of passage D following oven 122 or the like (optionally with a protective gas atmosphere). Depending on the desired heating strategy, the steel sheet strip 210 with the inductors 121 z. B. Curie temperature and then in the oven 122 warmed up to austenitizing temperature or already with the inducers 121 be heated to Austenitisierungstemperatur. In the oven 122 the Austenitisierungstemperatur is then held, so that in the steel strip 210 forms a homogeneous austenitic structure. (As described above, it may be provided that the steel strip 210 even partially heated and / or austenitized.)

The austenitized sheet steel strip 210 is then at the third station (precooling station) 130 Pre-cooled, what this station 130 multiple nozzle bars (the nozzle bars may also be on the bottom or both sides), which is a one-sided (or two-sided) nozzle array 131 form, and at least one pair of cooling rollers with cooling rollers arranged on both sides 132 has (the cooling rollers 132 are with back-up rolls 133 supported). The pre-cooled steel sheet strip 210 will be at the fourth station (board cutting station) 140 with a punch 141 divided into single board-like boards. From the boards are in the fifth station (forming station) 150 Molded sheet metal parts shaped, trimmed and form calibrated, with a cooling to the extraction temperature. The hot formed sheet metal parts 230 can then z. B. be removed with a robot.

The fifth station 150 exemplifies five press tools 151 . 152 . 153 . 154 . 155 formed as transfer tools and installed in a single press or in several presses of a press line. In the first tool 151 Forming boards are produced from the supplied board-like boards. In the second tool 152 the forming blanks are hot formed and optionally perforated. In the third tool 153 a trimming is carried out to produce the outline or outline contour and possibly a punch. (For punching and / or trimming, the sheet metal part temperature should be at least 300 ° C.) In the fourth tool 154 and fifth tool 155 The sheet metal parts are then cooled and simultaneously form calibrated, the cooling process is divided into two tools to achieve short cycle times. The first two tools 151 . 152 are heated and the last three tools 153 . 154 . 155 are cooled. Preferably, a temperature control for the tools is provided for the purpose of targeted temperature control.

The temperatures specified below the stations or tools correspond to possible preferred target temperatures for the sheet steel strip or sheet metal parts produced therefrom.

The attachment 100 has a comparatively short length compared to conventional systems. By an L arrangement in which the fifth station 150 at the board cutting station 140 offset to the tape running direction in an approximately 90 ° angle (as illustrated by the dashed angle), the space requirement can be significantly reduced again.

In the 2 shown attachment 100a has a forming station 160 with a follow-on composite tool group. The follow-on composite tool group includes, by way of example, three tool stages 161 . 162 . 163 which are installed in a press. Unlike the in 1 embodiment shown is the pre-cooled steel sheet strip 210 fed without board cut directly this follow-on composite tool group. In the first tool stage 161 The sheet metal parts are formed and possibly already perforated and partially trimmed. In the second tool stage 162 The sheet metal parts are cut and possibly perforated. In the third tool stage 163 The sheet metal parts are cooled, form calibrated and from the carrier strip 240 cut free. Follow-on tools allow due to the carrier strip 240 a very exact positioning and positioning accuracy. The first tool level 161 is heated. The second tool level 162 and the third tool level 163 are cooled. Again, a temperature control for the tools is preferably provided. The attachment 100a has fewer stations and an even shorter length. The pre-cooling station 130 may comprise at least one cooling roll, as in 1 shown.

LIST OF REFERENCE NUMBERS

100

investment

100a

investment

110

Station (unwinding station)

120

Station (warming station)

121

Inductor (s)

122

oven

130

Station (pre-cooling station)

131

nozzle array

132

chill roll

133

supporting roll

140

Station (board cutting station)

141

shears

150

Station (forming station)

151

Tool

152

Tool

153

Tool

154

Tool

155

Tool

160

Station (forming station)

161

tool level

162

tool level

163

tool level

210

Steel band

220

coil

230

Sheet metal part

240

carrier strip

D

Direction of the production flow

RT

room temperature

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 102009012940 B4 [0004]
• DE 102009016027 A1 [0005]
• DE 102014211241 A1 [0016]

Claims (10)

Method for mass production of hot-formed sheet-metal shaped parts (230), wherein the following steps are carried out at the stations (110, 120, 130, 140, 150) of a production line in the direction of the production flow (D): Unwinding a steel strip (210) from a coil (220); - Heating the steel strip (210), so that forms an austenitic structure; - Pre-cooling of the steel strip (210); - Producing boards from the pre-cooled steel sheet strip (210); - Hot forming of the boards to sheet metal parts (230), trimming the sheet metal parts and form-calibrating the sheet metal parts using a plurality of successively arranged tools (151, 152, 153, 154, 155), wherein simultaneous cooling takes place during hot forming, trimming and / or mold calibration. Method according to Claim 1 , characterized in that the boards are produced by means of a cutting shear (141). Method for mass production of hot-formed sheet-metal shaped parts (230), wherein the following steps are carried out at the stations (110, 120, 130, 160) of a production line in the direction of the production flow (D): Unwinding a steel strip (210) from a coil (220); - Heating the steel strip (210), so that forms an austenitic structure; - Pre-cooling of the steel strip (210); Feeding the precooled steel strip (210) to a progressive tool group (160) having a plurality of tool stages (161, 162, 163) for hot forming the steel strip (210) into sheet metal parts (230), trimming the sheet metal parts, shape calibrating the sheet metal parts, and free cutting the sheet metal parts in at least one tool stage (161, 162, 163) a simultaneous cooling takes place. Method according to one of the preceding claims, characterized in that the heating of the steel strip (210) takes place inductively. Method according to one of the preceding claims, characterized in that the pre-cooling of the steel strip (210) by means of at least one nozzle array (131) and / or by means of at least one cooling roller (132). Method according to one of the preceding claims, characterized in that the steel strip (210) is cleaned during pre-cooling or after pre-cooling. Method according to one of the preceding claims, characterized in that the steel sheet strip (210) has a zinc coating. Plant (100) for the series production of hot-formed sheet metal parts (230) with the following stations arranged in the direction of the production flow (D): - a station (110) for unwinding a steel strip (210) from a coil (220); - a station (120) for heating the steel strip (210); - a station (130) for pre-cooling the steel strip (210); - a station (140) for producing blanks from the precooled sheet steel strip (210); - A station (150) for hot forming the boards to sheet metal parts (230), trimming the sheet metal parts and form calibrating the sheet metal parts. Annex (100) to Claim 8 characterized in that the station (150) for hot working, trimming and shape calibrating to the other stations is arranged in an L-arrangement. Plant (100a) for the series production of hot-formed sheet metal parts (230) with the following stations arranged in the direction of the production flow (D): - a station (110) for unwinding a steel strip (210) from a coil (220); - a station (120) for heating the steel strip (210); - a station (130) for pre-cooling the steel strip (210); - A station (160) with a follow-on composite tool group (161, 162, 163), for hot forming the steel strip (210) to sheet metal parts (230), trimming the sheet metal parts, form calibrating the sheet metal parts and free cutting of sheet metal parts.

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